The present invention relates to a mechanism for determining the accuracy of a timepiece such as a watch. Such a mechanism has particular utility in the case of timepieces which include a receiver for receiving radio signals from an external source corresponding to the accurate time of day, which signals are compared with internal signals generated within the timepiece indicative of the time of day displayed by the timepiece.
A detection device of this type is known from the article by H. Effenberger, "Radio-Signal Timepiece Controlled by Microprocessors With Analog Display" in a book entitled Radio Signal Timepieces, edited by W. Hilberg (pp. 105-107). It is disclosed therein that a reflectable light beam be established in the face of the timepiece in such manner that when the hour and minute hands are oriented to shade an optoelectronic receiver system, a signal is generated whereby the fact that one of these hands has been rotated at this instant into a predetermined angular position is detected. A disadvantage of a detection device of this type is that both the hour and minute hand must be capable of being rotated independently of each other, i.e., they must be driven by separate stepping motors or by means of change gears. This raises the cost of the manufacture and operation of a timpiece of this type and in particular, in case of change gears, also the vulnerability of the clock mechanism. A further disadvantage of the known detection device is that, as the result of scattered light influences, it is difficult to identify the exact light-blocking position of the hands. Also, hands of different widths may lead to different signal actuation times. Open-work perforated hands, such as those found in fashion watches, may even produce multiple signals and thus erroneous evaluations, which may be compensated for only by means of particularly expensive electronic correction devices in order to insure the high display accuracy expected by consumers from a radio signal timepiece. The design of the face of a radio signal timepiece may be complicated by the need for arranging the optical sensor into the minute works in a highly visible manner, so that hands of different lengths are able to pass over it.
In view of these facts, it is an object of the invention to provide a detection device of the abovementioned type, wherein it is unnecessary to position sensors in visually disadvantageous locations, and wherein no restrictions are placed on the design of the hands.
Another object is to improve the operational safety of such a device.